#include<bits/stdc++.h>
using namespace std;
#define ll long long

struct fenwick {
    ll* bit;
    int fsize;

    void init(int n){
        bit = new ll[n+1];
        fsize = n;
        for (int i = 1; i <= n; i++){
            bit[i] = 0;
        }
    }

    int lsb(int x){
        return x&(-x);
    }

    ll query(int v){
        ll sum = 0;
        while (v > 0){
            sum += bit[v];
            v -= lsb(v);
        }
        return sum;
    }

    void add(int v, ll delta){
        v++;
        while (v <= fsize){
            bit[v] += delta;
            v += lsb(v);
        }
    }

    ll calc(int l, int r){
        return query(r+1) - query(l);
    }
};

void solve(){
    ll n, m, x;
    cin >> n >> m >> x;

    vector<ll> z(n);
    for (int i = 0; i < n; i++){
        cin >> z[i];
    }
    for (int i = 0; i < m+6; i++){
        z.push_back(0);
    }
    n += m+5;

    fenwick fn;
    fn.init(n);

    deque<pair<ll,ll>> q;

    for (ll i = 0; i < n; i++){
        q.push_front({z[i], i});
        ll lb = max(0ll, i+1-m);
        ll have = fn.calc(lb, i);
        while (q.size()){
            pair<ll, ll> bck = q.back();
            if (bck.second > i-m) break;
            q.pop_back();
        }
        //cout << i << ": ";
        //for (int i = 0; i < n; i++){
         //   cout << fn.calc(i, i) << " ";
        //}
        //cout << "\n";
        //cout << lb << " " << i << " " << have << "?";
        ll need = x-have;
        if (need <= 0) continue;
        while (q.size() && need > 0){
            pair<ll,ll> frnt = q.front();
            q.pop_front();
            ll by = min(frnt.first, need);
            frnt.first -= by;
            need -= by;
            if (frnt.first > 0) q.push_front(frnt);
            fn.add(frnt.second, by);
        }

    }
    //cout << "\n";
    //for (int i = 0; i < n; i++){
     //   cout << fn.calc(i, i) << " ";
    //}
    //cout << "\n";
    cout << fn.calc(0, n-1) << "\n";

}

int main(){

    int t = 1;
    //cin >> t;
    for (int i = 0; i < t; i++) solve();

    return 0;
}